Defect in the gamma polypeptide chain of a congenital abnormal fibrinogen (Paris I)

Abstract

THE primary physiological function of fibrinogen is fibrin clot formation, a process that requires three distinct reactions. Thrombin first cleaves fibrinopeptides A and B from two of the three pairs of polypeptide chains (Aα, Bβ, γ) of fibrinogen¹, following which the remaining fibrin monomers polymerise spontaneously into an insoluble fibrin clot². Thrombin also converts Factor XIII to an active form, called plasma transglutaminase³, which in turn catalyses the formation of covalentγ-glutamyl-ε-lysine isopeptide bonds⁴ between two γ chains and more than two α chains of different fibrin molecules⁵. The resultant γ chain dimers and α chain polymers crosslink the fibrin network and render it resistant to chemical or physical modifications.